JPH07214114A - Mill for expanding/rolling seamless tube and method therefor - Google Patents

Abstract

PURPOSE:To improve the dimensional accuracy of tube at the time of rolling a thin large-diameter tube having small wall-thickness to outside diameter ratio and to avoid the fin flowing due to the flaring of a stock tube. CONSTITUTION:In an expanding/rolling mill 10 provided with a pair of conical rolling rolls 81, 82, the mill has guide shoes 84 which are made so as to be tiltable to the rolling direction of a tube and the variation of shoe clearance by this tilting is set so that the variation on the outlet side of the mill is larger than the variation in the gorge part of the rolling roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe rolling mill for a seamless pipe such as a seamless steel pipe and a pipe rolling method.

[0002]

2. Description of the Related Art The Mannesmann method is the mainstream manufacturing process for seamless pipes, and it is roughly classified into a plug mill method and a mandrel mill method depending on the rolling method. Basically, a round billet is punched. It consists of a piercing step, a drawing and rolling step of thinning and drawing the pierced hollow shell, and a finish rolling step of squeezing the drawn and rolled hollow shell to a predetermined outer diameter or a constant diameter.

The plug mill method is a method generally used for manufacturing medium diameter seamless pipes. In this method, a round billet is heated in a heating furnace and pierced and rolled by a Mannesmann piercer, which is an inclined rolling machine, to form a hollow shell. The obtained hollow shell is further thinned and expanded by an elongator mill, which is also an inclined rolling machine, and further thinned and reduced by a plug mill having a pair of hole-type rolling rolls, and then inclined. The reeler mill, which is a rolling mill, expands the pipe with a slight reduction in the wall thickness and polishes the inner and outer surfaces of the pipe.
After being reheated, the shell rolled by the reeler is made into a product after being subjected to a constant diameter in a sizer mill.

FIG. 8 is an explanatory diagram showing an example of changes in the outer diameter of the rolled material on the delivery side of each rolling step of the above-described plug mill rolling line. In both the elongator mill for thinning and expanding the hollow shell and the reeler mill for polishing by thinning and expanding, the expansion ratio is at most several% to 17,18
Since it is about%, billets having various kinds of outer diameters are required to obtain a product having a wide range of outer diameters, which is one factor that hinders productivity. Therefore, in recent years, for the purpose of reducing the material billet size and simplifying the equipment, there has been proposed a pipe rolling schedule in which the pipe is expanded more than before in the drawing process.

However, in an inclined rolling mill having a barrel type roll shape such as the conventional elongator mill and reeler mill, when attempting to expand the hollow shell to a high extent, the blank tube is not caught properly and slips out. Or it is known that the hollow breaks due to flaring.
Here, high expansion means that the expansion ratio E _r is 0.2 or more. Generally, in piercing rolling with barrel type rolls arranged at an inclination angle β, the roll diameter gradually decreases on the exit side from the gorge portion and the peripheral speed becomes slower, so the wall thickness is reduced and the cross-sectional area decreases It is said that the rolling material is in a state of being braked, and as a result, the rolling material is twisted and additional shear strain is generated in the cross section.

In recent years, in order to solve these problems and expand the pipe more than ever, a pipe rolling method using an inclined rolling mill using a cone-type roll having a cross angle has been proposed. In the inclined rolling in which the cone-shaped rolls are inclinedly arranged at a constant advancing angle β, and the inclination rolling is performed by intersecting the pass line at the crossing angle γ, the roll diameter gradually increases toward the rolling-out side, and the peripheral speed increases. This is because there is no brake applied to the rolled material, and it is possible to prevent twisting of the rolled material and additional shear strain in the cross section.

For example, Japanese Patent Publication No. 3-77005 is characterized in that the crossing angle as shown in FIG. 9 is set to 2 ° to 35 ° and the contour line of the roll is composed of a conical entry portion and a rotating hyperboloid portion. A diameter expansion rolling mill has been proposed. According to this method
According to the company, the intermediate heating step, which is originally required, is no longer required, and thin large-diameter steel pipes can be manufactured at low cost.

On the other hand, Japanese Examined Patent Publication No. 5-38647 discloses a plug having two or more rolls each having a truncated conical diameter portion, an enlarged diameter portion and a sizing portion and a reeling portion as shown in FIG. With a cross-type inclined rolling mill equipped with at least the following, the roll surface angle α ₂ of the expanding portion is set to α ₂ > 5 °, the roll surface angle α ₃ of the sizing portion is set to α ₃ <α ₂ , and 0 ° ≦ α ₃ ≤10 °
And the reeling portion of the plug is arranged to face the sizing roll surface, and the reeling surface angle is approximately matched with the sizing portion roll surface angle α ₃ to perform pipe expanding piercing rolling or pipe expanding rolling. Is proposed. According to this method, it is possible to set the reeling portion of the plug to be long, and it is possible to improve the slip-out property, and as a result, it is possible to suppress the occurrence of uneven thickness and variation in outer diameter.

[0009]

However, as a result of diligent research by the present inventors, the use of a cone-type roll enables a higher expansion of pipes as compared with the case of using a barrel-type roll. If only the provided cone-shaped roll is used, the outer diameter of the front and rear end portions of the material to be rolled greatly varies compared with the outer diameter of the steady portion, which causes a problem that the dimensional accuracy deteriorates. In particular, when attempting to roll into a thin, large-diameter pipe with a small wall thickness outer diameter ratio (t / D), the outer diameter of the rolled material becomes large at the leading and trailing ends of the rolling compared to the steady part, and in some cases Causes flaring, bites into the gap between the roll and the shoe, and breaks, or the rolling cannot be continued.

Here, the cause of the fluctuation of the outer diameter on the leading end side and the trailing end side of the rolled material is as follows. The material rolled in the steady part is constrained by the material before and after rolling, or the material after rolling is continuous before and after rolling, but at the front and rear ends, there is no constraint from the front or back,
This is because the material tends to spread in the circumferential direction rather than advancing forward, the outer peripheral length increases, and the outer diameter increases as a result. Then, the occurrence of flaring due to the outer diameter variation at the front and rear ends becomes more remarkable in high tube rolling.

In order to solve this flare, for example, in Japanese Patent Laid-Open No. 5-123714, as shown in FIG. 11, the rotating shafts of the disc roll type shoes arranged on both sides of the rolling region sandwiched by the rolling rolls are covered with the disc rolls. A rolling mill has been proposed in which a guide shoe is mounted on a guide holder that is axially supported at one side of a disc roll, which is the direction of rolling entry of the rolled material, to reduce the gap between the disc roll and the rolling roll. There is.

However, in the prior art disclosed in Japanese Patent Laid-Open No. 5-123714, since the guide shoe is installed only on the side where the disk roll enters the material to be rolled, it is possible to prevent biting by flaring on the side where the guide shoe is installed. However, it is not possible to prevent the flaring from occurring due to the variation in the outer diameter of the front and rear ends.

Accordingly, the wall thickness outer diameter ratio (t / D) can be particularly improved by the inclined rolling mill using the cone type rolls having the intersecting angle.
It has been desired to improve the tube dimensional accuracy when rolling a small-diameter thin-walled large-diameter tube and to prevent the bare tube from biting due to flaring.

The present invention improves the pipe dimensional accuracy when rolling a thin-walled large-diameter pipe having a small wall-thickness outer diameter ratio (t / D) and avoids biting out of the raw pipe due to flaring. The purpose is to do.

[0015]

According to a first aspect of the present invention, a pair of cone type rolling rolls are arranged at a predetermined advance angle β with respect to a pass line, and an entrance side angle with respect to the pass line. The hollow element is arranged by intersecting the pass line at an intersecting angle γ so as to have α ₁ and a flank angle α _2, and arranging a pair of guide shoes on both sides of the rolling region sandwiched by the pair of cone-type rolling rolls. In a seamless pipe rolling mill that expands the pipe, the guide shoe can be tilted with respect to the rolling direction of the pipe, and the amount of change in the shoe gap due to this tilt is greater than the amount of change in the rolling roll gorge. The amount of change on the side is set to be larger.

According to a second aspect of the present invention, a pair of cone type rolling rolls are inclinedly arranged with respect to the pass line at a constant advance angle β, and the entrance side angle α ₁ with respect to the pass line.
And a cross-out angle γ with respect to the pass line so as to have an emergence angle α ₂ and a pair of guide shoes are arranged on both sides of the rolling region sandwiched by the pair of cone-type rolling rolls. In the seamless pipe rolling method of expanding the pipe, the guide shoe is tilted with respect to the rolling direction of the pipe at the front end and the rear end of the material to be rolled, and the change amount of the shoe gap due to this tilt is
The amount of change on the delivery side of the rolling mill is set to be larger than the amount of change on the rolling roll gorge portion.

[0017]

[Operation] Generally, in order to prevent the outer diameter of the material to be rolled from varying, the outer diameter of the material after rolling is changed by (1) changing the shoe gap, (2) changing the roll gap, 3)
A method of changing the plug diameter is known. this house,
What can be carried out during rolling are (1) and (2), but (2)
Since the thickness of the rolled material also changes with method (3), only (1) is practically possible.

However, as a method of changing the shoe gap in the above (1), conventionally, the entire shoe is moved in parallel to the pass line. However, if the shoe gap is too narrowed or widened too much, there is a risk of defective leading edge engagement and defective trailing end trailing.

As a result of detailed investigations by the inventors of the present invention, the relationship between the shoe gap and the outer diameter of the material to be rolled, and the relationship between the shoe gap and the occurrence of defective tip engagement and trailing edge trailing edge failure were found.
(1) The outer diameter of the material to be rolled can be controlled by the gap at the rolling exit side of the shoe, and (2) the gap at the rolling exit side of the shoe can cause defective tip engagement and trailing edge slippage. It was found that it had almost no effect.

Based on the above knowledge, by changing the shoe gap at the rolling exit side without changing the shoe gap at the rolling roll gorge position, it is possible to prevent defective leading edge and defective trailing end slipping. It has been found that the outer diameter of the material to be rolled can be controlled without causing it.

That is, in the tube rolling mill 10, the cone type rolls 81 and 82 are inclinedly arranged at a constant advancing angle β, and the rolls are passed so that they have an entrance side angle α ₁ and an exit side angle α ₂ with respect to the pass line. By arranging the rolls at an intersecting angle γ, the roll diameter is temporarily increased toward the rolling-out side and the peripheral speed is increased. As a result, the brake exerted by the rolls on the rolled material is eliminated. Therefore, in the inclined rolling by the pipe rolling mill 10, there is no twist of the material to be rolled due to the brake exerted on the material to be rolled by the roll, and additional shear strain in the cross section does not occur. It is possible to expand the hollow shell highly without causing failure of the tail and hollow breakage due to flaring. A plug 86 is arranged at the center of the rolling area formed by both rolling rolls 81 and 82.

Further, in the pipe rolling mill 10, a pair of guide shoe holders 83 are arranged on both sides of the rolling region sandwiched by the pair of cone type rolling rolls 81 and 82, and the guide shoes 84 are attached to and detached from the guide shoe holders 83. I made it possible. The guide shoe holder 83 has a tilting fulcrum 83A on the rolling-in end surface, and can largely tilt the exit-side end surface. As a result, the guide shoe holder 83
The guide shoe 84 provided at the position is tiltable with respect to the rolling direction of the pipe, and the amount of change in the shoe gap due to this tilt is smaller on the rolling mill exit side than on the rolling roll gorge. It will be set to be large.

Therefore, in the tube expanding and rolling mill 10, when the hollow shell is expanded and rolled, the front end and the rear end of the material to be rolled are
The guide shoe 84 is tilted with respect to the rolling direction of the pipe, and the change amount of the shoe gap due to this tilt is set so that the change amount at the rolling mill exit side is larger than the change amount at the rolling roll gorge portion. Be driven.

When the guide shoe 84 is tilted as described above, the amount of change in the shoe gap on the rolling-out side is larger than the amount of change in the shoe gap at the rolling roll gorge portion. For example, the tilt fulcrum 83A is not limited to the one shown in FIG. 2 and may be any one shown in FIGS. 6 (A) and 6 (B).

At this time, in the tube rolling mill 10, the outer diameter variation state at the front and rear ends when the outer diameter control is not performed is grasped in advance for each rolling condition such as the size of the material to be rolled ( 4), the tilt angle of the guide shoe 84 is controlled so as to eliminate the outer diameter variation at the front and rear ends. Since there is a constant relationship between the change in outer diameter of the material to be rolled and the change in shoe gap, the tendency for the outer diameter to increase at the front and rear ends of the material to be rolled can be eliminated by reducing the shoe gap. The tilt angle amount of the guide shoe 84 with respect to (shoe gap adjustment amount) is uniquely determined in advance as shown in FIG.

An example of the tilt control mechanism of the guide shoe 84 is as follows (FIG. 12 (A),
(B)).

That is, for example, the guide shoe holder 83 has a reduction cylinder 91 and a fulcrum 93 for adjusting the guide shoe gap.
Is rotatably connected with the tilting reduction cylinder 92.
Further, it is rotatably connected at a fulcrum 94 via a yoke 95 rotatably connected to the reduction cylinder 91 at a fulcrum 96. The gap between the guide shoe holder 83 and the guide shoe 84 moves horizontally by moving the reduction cylinder 91 up and down, and the guide shoe gap can be adjusted. Further, by raising and lowering the tilting reduction cylinder 92, the guide shoe holder 83 and the guide shoe 84 rotate about the fulcrum 93 and can tilt.

The inventors of the present invention have confirmed the occurrence of defective biting of the material to be rolled, defective slippage of the rolled material, and breakage of the hollow due to flaring when the hollow shell is expanded and rolled by the cone type rolls arranged in a crossed manner. As a result of a detailed study, a pair of cone-shaped rolling rolls were arranged at a certain advancing angle β with respect to the pass line, and the entrance side angle α ₁ with respect to the pass line.
Upon cross arranged with cross angle gamma, a high pipe expansion a hollow shell against the pass line so as to have a side angle alpha ₂ out and,
Set β, γ, β + γ in the following range, and 5 ° ≤ β ≤ 25
°, 10 ° ≦ γ ≦ 40 °, 20 ° ≦ β + γ ≦ 50 ° and α ₁ , α
Set ₂ to the following range and 0.5 ° ≤ α ₁ ≤ 5
°, 3 ° ≤ α ₂ ≤ 10 °, α ₁ ≤ α ₂ , and the thinning rate R _t
And the expansion ratio E _r , 1 ≤ E _r / R _t ≤ 3, where R _t
= (T _i -t _o ) / t _i , E _r = (D _o -D _i ) / D _i , t
_i : inlet side hollow shell thickness, D _i : inlet side hollow shell outer diameter, t
By satisfying the relations of _o : outlet pipe wall thickness, D _o : outlet pipe outer diameter, it is possible to remarkably prevent the occurrence of bite failure, defective tail slippage, and hollow breakage due to flaring, yield, and productivity. It was found that high pipe rolling can be performed without hindering the above.

[0029] That is, the cone-type roll, as shown in FIGS. 1 to 3 GORE - di section diameter D _R is 700 mm, the roll barrel length L
_R is 600 mm, roll length L ₁ from the entrance end to the gorge part
Is 250 mm, the entrance side angle α ₁ is 3 °, the exit side angle α ₂ is 5 °,
It is an inclined rolling mill with a crossing angle γ of 20 ° and a lead angle β of 15 °. It uses a hollow shell with a diameter _DH of 80 to 120 mm and a wall thickness t _H of 15 to 40 mm as the material to be rolled, and the roll gap E and the plug are advanced. The amount L was variously changed and the wall-thickness reduction ratio R _t and the pipe expansion ratio E _r were changed for pipe expansion rolling, and the occurrence of hollow biting due to defective biting and flaring was investigated. FIG. 7 shows the results organized by taking R _{t on} the horizontal axis and E _r on the vertical axis.

As is clear from the figure, a pair of cone type rolling rolls are arranged at a constant advancing angle β while being inclined by γ
In the slant rolling method of the pipes which are crossed with each other, the thinning rate R _t
And tube expansion ratio E _r in the range of 1 ≤ E _r / R _t ≤ 3, it is possible to avoid defective biting, defective slippage, and hollow breakage due to flaring, and the degree of freedom in rolling setting is improved. It is possible to raise it.

In the present invention, 5 ° ≦ β ≦ 25 °, 10 ° ≦
The reason for setting γ ≦ 40 ° and 20 ° ≦ β + γ ≦ 50 ° is as follows. Within a certain range, the larger the advancing angle β, the crossing angle γ, and the sum β + γ, the more the twist of the material to be rolled and the additional shear strain in the cross section can be reduced, which prevents the hollow tear due to flaring. Effective against
However, β <5 °, or γ <10 °, or β + γ <20
If the angle is °, the effect is not sufficient and hollow breakage due to flaring tends to occur. Therefore, the lower limit of β is 5 °, γ
The lower limit of is 10 °, and the lower limit of β + γ is 20 °. On the other hand, β>
At 25 °, or γ> 40 ° or β + γ> 50 °, the twist of the material to be rolled increases in the opposite direction, and additional shear strain in the cross-section also occurs in the opposite direction, rather causing hollow tearing due to flaring. It tends to occur. Therefore, β is 25 ° and γ is
40 ° and β + γ shall not exceed 50 °.

The reason why 0.5 ° ≦ α ₁ ≦ 5 ° is set is as follows. The entrance side angle α ₁ has an important influence on the biting property of the material to be rolled. If α ₁ exceeds 5 °, the material to be rolled is rapidly reduced during biting, and the drag force from the rolling roll required for deformation exceeds the thrust in the forward direction transmitted from the rolling roll. . Therefore, α ₁ is 5 °
Shall not be exceeded. On the other hand, if α ₁ becomes too small, it is necessary to considerably lengthen the roll barrel on the inlet side in order to obtain the outer diameter reduction of the material to be rolled necessary for the thrust in the forward direction. Becomes higher and not practical. Therefore, the lower limit of α ₁ is 0.5 °.

The reason why 3 ° ≦ α ₂ ≦ 10 ° is set is as follows. The larger the flank angle α ₂ is, the shorter the roll barrel on the exit side, which is necessary for the amount of pipe expansion, and the equipment can be downsized, but if it is too large, hollow breakage due to flaring will occur. Is likely to occur.
Therefore, α ₂ shall not exceed 10 °. On the other hand, α ₂
If is too small, it is necessary to lengthen the roll barrel on the outlet side considerably in order to obtain a predetermined amount of pipe expansion, resulting in high facility construction cost and impracticality. Therefore, the lower limit of α ₂ is 3 °.

The reason why α ₁ ≦ α ₂ is set is as follows.
When the exit side angle α ₂ becomes smaller than the entrance side angle α ₁ , in order to obtain a predetermined pipe expansion amount, the roll barrel length is longer than that when the exit side angle α ₂ is larger than the entrance side angle α _1. Becomes relatively long. Therefore, α ₁ does not exceed α ₂ .

[0035]

1 is a plan view showing an inclined rolling mill according to the present invention, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a front view seen from the rolling direction of FIG.

In the inclined rolling mill 10 shown in FIGS. 1 to 3, a pair of cone type rolling rolls 81 having a gorge diameter D _R ,
82 is inclinedly arranged at a constant advance angle β with respect to the pass line, and is also arranged at a crossing angle γ with respect to the pass line so as to have an entrance side surface angle α ₁ and an exit side surface angle α _2, and both rollings are performed. A guide shoe holder 83 and a guide shoe 84 are arranged on both sides of the rolling area formed by the rolls 81 and 82.
In the rolling rolls 81 and 82, the portion of the diameter D _R is an inflection point of the diameter change in the roll axial direction, and the diameter D _R is matched with the gorge portion. And both rolling rolls 81, 82
The plug 86 was disposed between the two, and the hollow shell 1A was tilt-rolled at the gorge portion roll gap E of both rolling rolls 81 and 82 to obtain the hollow shell 1B after pipe rolling.

At this time, in the example of the present invention, 5 ° ≦ β ≦ 25
°, 10 ° ≦ γ ≦ 40 °, 20 ° ≦ β + γ ≦ 50 °, 0.5 ° ≦ α
₁ ≦ 5 °, 3 ° ≦ α ₂ ≦ 10 °, and α ₁ ≦ α ₂ .

Further, the wall-thickness reduction ratio R _t and the pipe expansion ratio E _r are defined as 1 ≦
E _r / R _t ≤3.

The operation and effect of this embodiment will be described below. That is, the cone type rolling roll shown in FIG. 1 has a gorge portion diameter D _R of 1000 mm, a roll barrel length L _R of 900 mm, a roll length L ₁ from the entrance end to the gorge portion of 300 mm, and an entrance side surface angle α ₁ of 3 °, flank angle α ₂ is 10 °, crossing angle γ is 30
Is an inclined pipe rolling mill with a tilt angle β of 15 ° and a diameter of 192m.
A hollow shell with a wall thickness of 12 mm and a wall thickness of 267 m
The pipe was expanded and rolled to have a wall thickness of 7 mm and a thickness of 7 mm, and the outer diameter distribution in the longitudinal direction of the rolled pipe was measured. Fig. 4 shows the outer diameter distribution after the tube-expansion rolling by the conventional method. The outer diameter is large at the rolling front end and the rolling rear end. On the other hand, in response to the outer diameter variation after the tip, the shoe 84 is rotated around the inlet end face as a fulcrum to control the tilt angle of the shoe 84 as shown in FIG. By reducing the shoe spacing, it is possible to reduce fluctuations in the outer diameter of the material to be rolled as shown in FIG.

[0040]

As described above, according to the present invention, it is possible to improve the dimensional accuracy of a pipe when rolling a thin-walled large-diameter pipe having a small wall thickness outer diameter ratio (t / D), and to improve the raw pipe. It is possible to avoid biting out due to flaring.

[Brief description of drawings]

FIG. 1 is a plan view showing an inclined rolling mill according to the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a front view seen from the rolling direction in FIG.

FIG. 4 is a diagram showing a change in outer diameter of a material to be rolled in the longitudinal direction when the pipe is rolled and rolled by a conventional method.

FIG. 5 is a diagram showing a shoe tilting pattern when pipe rolling is performed by the method of the present invention and a variation in outer diameter in the longitudinal direction of the material to be rolled at that time.

FIG. 6 is a schematic view showing a modification of the tilt fulcrum position of the guide shoe.

FIG. 7 is a diagram showing a situation in which biting failure, tail failure, and hollow breakage due to flaring occur when tube rolling is performed while varying the wall thickness reduction rate and the tube expansion rate.

FIG. 8 is a diagram showing an example of changes in the outer diameter of the material to be rolled on the delivery side of each rolling step of the rolling line by the conventional plug mill method.

FIG. 9 is a schematic view showing a conventional inclined rolling mill.

FIG. 10 is a schematic view showing another conventional inclined rolling mill.

FIG. 11 is a schematic view showing still another conventional inclined rolling mill.

FIG. 12 is a schematic diagram showing an example of a guide shoe tilt control mechanism according to the present invention.

[Explanation of symbols]

 10 Tube expansion and rolling mill 81, 82 Rolling roll 84 Guide shoe 86 Plug

Claims (2)

[Claims] 1. A pair of cone type rolling rolls are inclinedly arranged with respect to a pass line at a constant advancing angle β, and a pass is formed so as to have an entrance side angle α ₁ and an exit side angle α ₂ with respect to the pass line. In a seamless pipe expansion rolling machine that expands a hollow shell, a guide pipe is installed at both sides of the rolling region sandwiched by the pair of cone type rolling rolls. The shoe can be tilted with respect to the rolling direction of the pipe,
The amount of change in the shoe clearance due to this tilting is set so that the amount of change at the rolling mill output side is larger than the amount of change at the rolling roll gorge section. Machine. 2. A pair of cone type rolling rolls are inclinedly arranged at a constant advancing angle β with respect to a pass line, and a pass is formed so as to have an entrance side angle α ₁ and an exit side angle α ₂ with respect to the pass line. In the pipe rolling method of a seamless pipe for expanding a hollow shell, a pair of guide shoes are arranged on both sides of the rolling region sandwiched by the pair of cone-type rolling rolls. At the leading and trailing ends of the rolled material, the guide shoes are tilted with respect to the rolling direction of the pipe, and the amount of change in the shoe gap due to this tilt is smaller on the rolling mill exit side than on the rolling roll gorge. A seamless pipe expanding and rolling method characterized by being set to be large.